Tyson Gay (left) and Justin Gatlin compete in a 100 semifinal at the 2013 U.S. championships at Drake Stadium in Des Moines on June 21. / Kirby Lee, USA TODAY Sports

by From staff reports, USATODAY

by From staff reports, USATODAY

U.S. sprint champion Tyson Gay has been notified by the U.S. Anti-Doping Agency that his sample tested positive for a banned steroid, according to the BBC Friday.

In a letter from USADA to Gay obtained by the BBC, the athlete was informed of an adverse analytical finding from a sample taken at the U.S. Championships, which also served as the world championship trials, in June.

The letter stated: "Using the Carbon Isotope Ratio Analysis it reported that the sample had an adverse analytical finding reflecting values that are consistent with the administration of a steroid of exogenous (external) nature."

The standard penalty for use of steroids, human growth hormone and other serious doping substances and methods is a two-year ban.

Gay announced in July he had tested positive for a banned substance and withdrew from the world championships, which were held earlier this month in Moscow. The result of the B sample test has not been released.

USADA released a statement Friday in response to questions about the positive test. "We appreciate Mr. Gay taking responsibility for his decisions and for voluntarily removing himself from the World Championships. As this is an ongoing case we have no other comment at this time," USADA CEO Travis Tygart said in a statement.

Gay won the 100 and 200-meter titles at the U.S. championships held in Des Moines in June. He said he tested positive in an out-of-competition test he took May 16. The Associated Press reported that he also failed a drug test at nationals.